Live brood in stump (6)

I believe the answer is:

bemuse

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'stump' is the definition.
Although both the answer and definition are verbs in their base form, I can't understand how they can define each other.

'live brood' is the wordplay.
'live' becomes 'be' (synonyms).
'brood' becomes 'muse' (I can't justify this - if you can you should believe this answer much more).
'be'+'muse'='BEMUSE'

'in' is the link.

Can you help me to learn more?

(Other definitions for bemuse that I've seen before include "Bewilder or baffle" , "Perplex" , "Puzzle and confuse" , "Stupefy, puzzle" , "Cause puzzlement" .)

I've seen this clue in The Irish Times.

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